A typical key structure provided to an electronic apparatus or the like includes a water stop member, such as an O-ring or a gasket, between a shaft portion of a key and a case of the electronic apparatus to implement a waterproof function between the key and the case. In another key structure, resilience is applied to a key using a coil spring so as to bring the key back to an original position when the force that pushes down the key is released. Such techniques are discussed in, for example, Japanese Laid-open Patent Publication No. 2004-95252 or Japanese Laid-open Patent Publication No. 2004-146163.